1. Field of the Invention
The present invention relates to a medical device for inserting medical instruments into a subject. In particular, the invention provides a vascular access needle assembly to facilitate insertion of a guide wire into a subject.
2. Background of the Invention
Medical instruments used for diagnostic or therapeutic purposes such as micropuncture, catheterization, and arteriography are often introduced into subjects through vascular vessels using various types of needle assemblies. One problem associated with the use of such needles is inadvertent needle sticks.
The insertion of catheters and other instruments into blood vessels typically involves inserting and removing guide wires. For example, micropuncture involves inserting and removing guide wires of increasing diameter in order to successfully insert diagnostic or therapeutic instruments which may have a greater diameter than the initial insertion point into the blood vessel. One procedure involves making an incision in the skin over the target blood vessel. A thin walled needle is then inserted into the blood vessel. A fine guide wire is then inserted through the needle and the needle is removed by sliding it over the end of the guide wire. A dilator having inner and outer components is then placed over the guide wire, and is advanced over the guide wire and into the blood vessel. The inner component of the dilator and the guide wire are removed while the sheath (the outer component of the dilator) remains in the blood vessel. A guide wire of a larger diameter may then be inserted into the blood vessel. In addition to consuming valuable time, the disadvantage of this procedure is that in order to insert a device of greater diameter than the needle, more than one guide wire must be inserted and removed from the blood vessel, increasing the chances of damaging the vessel wall.
Other access and/or tissue collection procedures also have potential problems associated with the use of complicated devices and limitations much like those of vascular access needles.
Thus, what is needed, but has not yet been provided, is a vascular access needle which allows the insertion of instruments of varying or increasing diameter into a blood vessel without requiring the insertion of multiple guide wires, and which protects against inadvertent needle sticks. What is also needed is an access device which allows for quick and easy insertion of instruments. What is also needed is a device that allows for tissue to be quickly and easily obtained for biopsies.